I don't have a use for a Chromebook myself (I'm a developer, need a PC/Mac) but if I walked outside with one, I'd simple power up my phone hotspot.
There are very few situations where I do not have a readily-available connection to the internet.
From my perspective a Chromebook can't do anything better than a Netbook or a Tablet other than keeping your data safe in the cloud rather than in jeopardy on a harddrive that could be stolen or broken. But you can use cloud storage on any PC or Tablet so I just don't see the point. Sure you can pay for extra data to use it away from WiFi, but a netbook or tablet keeps on chugging along even if the you loose data access.